Did you upgrade to a paid account on a mobile device, i.e. through Apple's App store or Google Play? If so, you need to manage your subscription through the store you subscribed in. Otherwise, contact Support and they'll assist with canceling your account.
If you just want to downgrade, you could just try the Downgrade page as listed in this help article and in one of the replies listed above.
[This thread is now closed by moderators due to inactivity. If you're experiencing a similar behavior, feel free to start a new discussion in the Find Answers section here. ]
